-ene cccc cccf ccee ccfc ccff ccnc ccne ccnf ccnr ccrc ccre ccrf cec- cece ceec cef- cefc cefn cen- cene cer- cerc cere cerf cern cexe cfcf cfcn cffr cfnr cfre cfrn cfrx cnex cnrc cnrr crcc crce crcr cre- crec cree cren crex crfc crne cxxx eccc ecce ecef ecfc ecfr ecne ecrc ecrf ecrr eeee eefe eefn eerc efen ence enee ener ennc enne er-x ercc erce erec eren erer erfc erfx erne errc erre exec exen exer exrx fccf fece feen feer fefc fefe feff fene fenn ferc fere fern ferr ffcc ffee ffff ffrr frcc frcn free fren frex frfc nccc nccf nccn nccr ncec ncee ncef ncen ncer ncfc ncfe ncnc ncrc ncre necc nece necr neef neen neer nefe neff nene nerc nere nerf nerr nexe nexx nfer nfff nnnn nren nrfc nrrc rccc rcfc rcnr recc rece recr reef reen refe reff refn refr rene renn rere rexx rfef rffc rrfc rrrr xeer xefe xen- xene xenn xer- xexe xfce xfer xnee xxxx